;;;###autoload
(defun apropos-variable (pattern &optional do-not-all)
"Show variables that match PATTERN.
-When DO-NOT-ALL is non-nil, show user options only, i.e. behave
-like `apropos-user-option'."
+With the optional argument DO-NOT-ALL non-nil (or when called
+interactively with the prefix \\[universal-argument]), show user
+options only, i.e. behave like `apropos-user-option'."
(interactive (list (apropos-read-pattern
(if current-prefix-arg "user option" "variable"))
current-prefix-arg))